A plunger lift system is a cost-effective way to maximize production returns on mature or underperforming oil and gas wells. Plunger lift removes liquid from the well using the well's own energy so production can be increased for the operator.
In a typical plunger lift system, a lubricator is attached to the wellhead and serves to catch a plunger, which travels in the well tubing, upon its arrival at the surface. During its travel cycle, a plunger alternately pushes a liquid column during its rise cycle and falls to a bottom hole spring location during the fall time so it may begin another cycle. An arrival sensor is attached to the lubricator and signals the controller when the plunger is at the surface. When the controller signals the well to close, the plunger falls to the bottom hole spring location. Although the bottom hole spring is typically positioned at the end of the well tubing, it may also be positioned at any point in the tubing string using a collar stop or a tubing stop. When the controller signals the well to open, the energy of the formation pushes the plunger and the liquid column toward the surface. Thus, arrival detection can be a major component of a plunger lift system. If an arrival sensor misses an actual plunger arrival, or falsely signals a plunger arrival, the well can easily load up and stop producing.
There are currently a variety of methods of detecting plunger arrival at the lubricator. Some of these methods utilize inductive sensors mounted to the wellhead. Acoustical sensors can also be used. Other of these methods take advantage of the magnetic state (or phase) of metal in the metal making up the plunger itself. For example, one method uses a coil to detect induced voltage changes as a moving magnetic field from the plunger moves past the coil. However, various operational factors, such as plunger speed, plunger position, its degree of rotation, the level and type of magnetism involved in the material of construction, and the applied magnetic field, can each affect the ability of a system to accurately detect plunger arrival. What is needed is a method and apparatus for integrating various sensor capabilities into a unit that provides a platform capable of reliably and accurately detecting actual plunger arrival to minimize production anomalies.
The disclosed device utilizes a magneto-inductive sensor apparatus to detect actual plunger arrivals, thus minimizing false positives in the detection of plunger arrivals. The microprocessor of the disclosed device allows for control of the resolution needed for the detection of a plunger without the typical issues found in an analog implementation. In addition, the disclosed device is capable of interfacing with a variety of generic or branded equipment types, thus providing for expansive employability.